Carburetor choice

On my 318 600 Holey vac secondary ,on the 340 750 edelbrock... id stick with 60 holley on your heavy automativc car, then step up to 650-750..dsee whaich works out better. You can get used stuff, my carbs have been bought used the holley 100 bucks, the eddy 150 at a swap meet. trial and error if you dont want to do tha math and even math guys screw it up, ever hear about the guy who opened the Summit catalog, bought every bolt on in the book and the car still didnt want to get out of its own way?...P.S. gas mileage is going to factor in, do you want to spend 50-100 bucks driving around for the weekend? two days?